The present invention relates to a heating device for heating a first medium which is in liquid state and/or frozen state.
In various kinds of vehicle there are reservoirs for liquids which are used for different functions of the vehicle. In certain cases there is a need to ensure that these liquids have a certain temperature to enable them to function as intended. The present invention can be applied in connection with the heating of liquids in various types of reservoirs for vehicle applications, but the following description will focus, for illustrative yet non-limiting purposes, on how the invention can be used to heat urea which is used to clean exhaust gases emanating from an internal combustion engine.
One way of satisfying the increasingly stringent requirements for the cleaning of exhaust gases emanating from internal combustion engines is to convert the exhaust gases into harmless or less harmful gases by the injection of an additive, such as urea.
The use of urea can serve, above all, to reduce the nitrogen oxides NOX content, thereby helping to cut emissions of harmful substances into the environment.
For this purpose, however, a continuous supply of urea is required whilst the internal combustion engine is running, which means that a vehicle, e.g., a truck, which is to utilize the cleaning technology in question is equipped with a reservoir for urea. Urea can then be supplied from the reservoir, for cleaning the exhaust gases.
There are, however, problems associated with the use of urea. In cold weather, for example, urea can freeze in the reservoir and/or in associated lines. If the urea freezes in the reservoir, this may mean, in turn, that urea cannot be provided as intended or that the urea which can be provided has a temperature which is unfavorable to the cleaning process or, in the worst case, that the reservoir is damaged as a result of frozen urea taking up a larger space than corresponding quantity of liquid urea.
It is desirable to provide a device for heating liquids, especially urea, in vehicle applications, which device allows such liquids to be used even where the ambient temperature is so low that the liquid is at risk of freezing in the reservoir and which device can be used to thaw the frozen liquid should the liquid have frozen.
According to an aspect of the present invention, a device for heating a first medium which is in liquid state and/or frozen state includes a reservoir disposed on an engine-driven vehicle and an element for heating the first medium present in the reservoir. The heating element is disposed inside the reservoir for direct heating of the first medium.
Positioning the heating element inside the reservoir for direct heating of the first medium, e.g., urea, allows an effective heating to be obtained at any chosen position in the reservoir.
In an advantageous embodiment of the invention, the heating element is configured as a coil for accommodation of a second medium to allow transfer of heat from the second medium to the first medium. It is especially advantageous to use as the second medium the liquid which is also used to cool the vehicle engine. By circulating coolant through the heating element, the first medium is heated, whilst, at the same time, the coolant temperature is able to be lowered, which in certain cases is beneficial. In this way, the first medium in the reservoir can therefore be supplied with heat from a heat source which, when the engine is running, is already available within the vehicle, this without the need to use any additional energy source, which, in turn, is a cost-effective way of attending to the heating of the first medium.